On most occasions, yes, it's a bad thing.
Pre-pitch, oxygen in the wort is a good thing. It helps facilitate yeast reproduction. However, oxygen after fermentation has begun or ended is not usually a good thing. Oxygen entering the beer during the later stages of the process can lead to oxidation and off flavors.
Do your best not to disturb the brew mate.
Oh crap. I'm sorry. I had no idea this was a wine question! My fault! Was just answering "Unanswered threads".
*scurries away*
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